The invention relates to a device for recognising characters in a document with at least two writing recognition units, an evaluation device for evaluating the results of the writing recognition units with the aid of a database of rules for evaluating the sample recognised by the writing recognition units. The invention also relates to a process for the recognition of characters which makes use of the device.
The recognition of character samples or written symbols is an ever important task in the modern business world. Data processing installations with character recognition units are used, particularly in the banking area and in other finance for reading remittance orders, cheque forms and other documents without the help of manual input.
There are in particular two character or writing recognition methods known in the Federal Republic which are on the market. The Computer Gesellschaft Konstanz mbH (CGK) process is marketed under the type reference "CSL 2610". AEG Elektrocom GmbH Erkennungssysteme has developed the "Polyform" character recognition software. This software is employed in the AEG readers and in equipment from other companies.
The two methods are based on different writing recognition algorithms and they can therefore be described as "orthogonal" to one another. This difference in the algorithm employed leads to the result that the two methods give different results for the same text. This variation in results is particularly noticeable in the case of handwritten text since the characters in such texts are often written very quickly and not clearly.
In order to improve the reliability of the writing recognition, tests have been carried out with a so-called "multi-voting" method where the results of reading of the same characters from several writing recognition units are supplied to an arbitration unit. The arbitration unit, as currently used, compares the results and frequently selects the overall result from the writing recognition process in accordance with the following rules:
1) If all writing recognition units come to the same result, then the result is trivial, i.e. the total result will be selected from any desired writing recognition unit. PA1 2) If none of the writing recognition units supplies a satisfactory result, the overall result is "reject" (not recognisable). PA1 3) If the results of all writing recognition units are the same, at least one of which has a reliability value greater than a fixed threshold value (e.g. 50%), the most reliable value is selected as the overall result. PA1 4) If the results of all writing recognition units are unequal, the overall result is "reject" (not recognisable). PA1 A first step for the recognition of the written character with the aid of at least two writing recognition units and the provision of reliability values; PA1 a second step for determining the confidence level for the character, PA1 a third step for testing the agreement of the results from the different writing recognition units, PA1 a fourth step for evaluating rules with the aid of the credibilities and agreements and PA1 a fifth step for supplying the overall result of the writing recognition process.
The "multi-voting" method only slightly improves the reliability of the writing recognition process compared with the conventional method. However, it requires the use of at least two writing recognition units which each use a different recognition algorithm. This is considerably more costly in terms of licence fees and the cost-benefit relationship is dubious.